Yuxin Li, Wenzhu Cui, Xiaoling Liu
Estrogen sulfotransferase (EST), a member of the sulfotransferase (SULT) family, catalyzes estrogen sulfation and regulates its activity and content. EST has been mainly studied in vertebrates. Our previous analysis of EST expression in kidney, hepatopancreas, mantle, adductor muscle, gill, and gonads of Chlamys farreri (C. farreri) revealed highest expression in the gonads, suggesting an important role in gonadal function. We knocked down EST by RNAi, examined gonadal histology and E2 levels (via ELISA), expressed recombinant EST in prokaryotes, and assessed its activity using a novel MCF-7 proliferation assay, where E2 promotes cell growth and EST inactivation reduces it. After EST knockdown, EST mRNA levels decreased by 67% in the ovary and 63% in the testis, indicating effective silencing. Histological analysis revealed that RNAi accelerated oocyte proliferation and development, enhanced oocyte vitellogenesis and delayed testicular development in the experimental group. Moreover, estradiol (E2) levels in both ovaries and testes were higher in the experimental groups than in the controls (p < 0.05). The recombinant EST protein was expressed as inclusion bodies and, after purification, denaturation, refolding, and ultrafiltration, yielded high-purity, concentrated protein. Enzyme activity assays showed a decreased proliferation rate of MCF-7 cells, indicating that EST possesses enzymatic activity that can inactivate E2. It is worth mentioning that the traditional isotope-labeling method for detecting EST activity is limited by high cost, operational complexity, technical demands, and potential health risks; therefore, this study established a simpler, more economical, and safer method for measuring EST enzymatic activity. In conclusion EST contributes to the maintenance of estrogen balance during gonadal development.